Voltage regulators of the switching type are in common use. Switching regulators are more efficient in their energy use than either linear series pass voltage regulators or linear shunt voltage regulators. The advantage of higher energy efficiency is extremely important in those applications in which large amounts of power are voltage regulated. For example, switching regulators could advantageously be used for the regulation of voltage for television transmitters, radar trarsmitters and the like.
Some types of radar transmitters produce pulses of relatively constant duration which recur at a fixed pulse recurrence rate or pulse recurrence frequency (PRF). The ratio of the radar pulse transmitting time to the inter-pulse period is termed the duty cycle. Modern high performance radar systems make use of the frequency and phase of the return or echo signal relative to the transmitted signal, and may operate in a mode in which the duty cycle may change from pulse to pulse. Thus, the load presented by the radar transmitter to its power supply in such a high performance radar system changes from moment to moment in a dynamic manner. These dynamic load changes may be of large magnitude, as for example when a radar system switches from a standby mode to a maximum duty cycle mode of operation.
The transmitters of high performance radar systems are extremely voltage sensitive, because the phase and frequency of the transmitted signal are affected by the transmitter power supply voltages. Consequently, the switching regulator must have an extremely wide dynamic range in order to maintain the regulated voltage within the required accuracy notwithstanding major variations in the duty cycle. It has been discovered that a major limitation in conventional pulse-width-modulated regulators is attributable to the length of time required to bring the current in the energy storage inductor from its idle current level (as from the standby condition) to the maximum current required for the highest duty cycles. It is desirable to improve the transient response of switching regulators.